Since the invention of lasers, optics made of glass, quartz, zinc selenide, germanium and numerous other focusing mediums shaped into the form of lenses have been used to concentrate the raw, unfocused laser beam onto targets of many types. Anti-reflective coatings have been developed and applied to the expensive optics to permit transmission of the laser beam through the lens medium. However, at extremely high powers, the unfocused laser beam rapidly degenerates the lens material.
A significant problem that occurs during the use of high-powered laser systems is the distortion of the laser beam and/or damage to the lens material. Since many of the advanced lens optics can cost hundreds or even thousands of dollars, lens damage creates a significant problem. Further, the removal and replacement of a damaged lens can result in large amounts of time lost during the actual replacement procedure.
Since current lenses are made from light-transmitting materials, environmental factors can have a large effect on the functionality of the lens. For example, humidity can create damage to the lens optics due to the condensation of water on the lens surface. Further, use of lens optics in warm environments requires the use of cooling systems.
In some applications of lasers including lenses made from light-transmitting materials, the laser is used in a harsh operating environment, such as a desert. In this type of operating environment, small particles of sand or other debris can scratch or damage the optics, thereby limiting the use of such devices.
In addition to the use of optics, alternate focusing devices include the use of mirrored focusing technology. Although mirrored focusing technology addresses some of the problems created by the currently available optics, mirrored focusing devices do not provide the required performance of costly optics. Therefore, a need clearly exists for technology to replace both optical focusing materials for lenses and mirrored focusing technology. The use of such improved technology would allow focusing devices to be used in many different operating environments, such as space where optics can be easily degraded by cosmic radiation and solar wind. Therefore, it is an object of the present invention to provide a laser focusing device that does not utilize lens optics. Further, it is an object of the present invention to provide a focusing device that provides the required focusing while being able to be used in a harsh operating environment. A still further object of the present invention is to provide a focusing device that can be manufactured at a relatively low cost and easily replaced upon damage.
The present invention is a lensless focusing device for focusing an input, raw laser beam to create a focused, useful output laser beam. The focusing device of the present invention eliminates expensive and fragile optics while focusing an input laser beam to a usable, focused output.
The focusing device of the present invention utilizes a solid body of preferably metallic material such as aluminum or stainless steel. The solid body extends from an inlet end to a discharge end.
The solid body includes a generally open interior that extends from an inlet opening formed at the inlet end of the solid body to a discharge opening formed at the discharge end of the solid body. The open interior is defined by a conical inner wall formed in the solid body that extends from the inlet opening to the discharge opening.
The inlet opening formed in the solid body defines an entry area that receives the input laser beam. Preferably, the entry area of the opening is greater than the cross-sectional area of the input laser beam such that the entire input laser beam can be received through the inlet opening.
As the individual light beams of the input laser beam enter the inlet opening, the light beams contact the conical inner wall and are reflected toward the discharge opening. Specifically, the inner wall of the solid body is a polished surface that reflects the light beams toward the discharge opening. The polished inner surface can be formed through many machining or application processes as long as the polished surface reflects the inlet light beams toward the discharge opening.
The discharge opening formed at the discharge end of the solid body has a discharge area that is less than the cross-sectional area of the input laser beam. Therefore, the discharge opening focuses the individual light beams of the input laser beam as required.
In an alternate embodiment of the invention, a heating element is positioned in contact with the solid body of the focusing device. The heating element is operable to elevate the temperature of the solid body during operation. The elevated temperature of the solid body increases the reflectivity of the conical inner wall to increase the efficiency of the focusing device. In the most preferred embodiment of the invention, the heating element is positioned within an opening formed in the solid body such that the heat generated by the heating element can be effectively transferred to the solid body.
In yet another alternate embodiment of the invention, the solid body is formed having a series of steps formed along the conical inner wall extending between the inlet opening and the discharge opening. Each of the steps formed along the conical inner wall decreases the diameter of the open interior as the steps proceed from the inlet opening to the discharge opening. The conical steps formed along the conical inner wall each include a polished surface such that the steps direct the light beams of the inlet laser beam toward the discharge opening.
In the most preferred embodiment of the invention, the discharge opening has either an oval or circular cross-section shape. However, it is contemplated that various other shapes for the discharge opening can be used depending upon the preferred shape of the focused laser beam.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.